Unable to send mails via Horde Webmail getting error “There was an error sender your message : Server Denied Authenication”

Solution:

Please note that what you are facing is the authentication issue connecting towards mail server. We suspect that your password is not complex due to which you are facing this error. We are unable to set the same password in the plesk as it is not complex, so we reset in the mail server directly and checked the sending of email, it is working with out any issue. In order to fix the issue permanently,Kindly reset the mail id password in the plesk control panel and use the generate password option in order to get complex password.